What opens what.
WHAT A DEFAULT IS
The program that opens a given type of file.
WHY IT MATTERS
Installing something frequently changes defaults without asking clearly.
WHAT THAT CAUSES
Files opening in the wrong program Web links opening in a browser you do not use
WHAT TO CHECK
The defaults for the file types you use most.
WHAT TO SET DELIBERATELY
Your browser Your document, spreadsheet and presentation programs Your image viewer Your portable document reader
HOW TO OPEN SOMETHING IN A DIFFERENT PROGRAM ONCE
Right-click, and choose to open with.
WHAT TO BE CAREFUL WITH
The option to always use that program, which changes the default permanently.
WHAT TO WATCH DURING INSTALLATION
Screens offering to make something your default.
WHAT TO DO
Read them rather than clicking through.
WHAT ELSE INSTALLERS ADD
Browser extensions Additional bundled software Startup entries
WHAT TO DECLINE
All of those, unless you want them.
